Building panel structure



Oct. 14, 1969 R. E. HAYES BUILDING PANEL STRUCTURE Filed Dec. 8. 1966 2Sheets-Sheet 1 INVENTOR.

5 HAY GS We ATTD 5Y5 fig-2a ZMRRWUMDMW Oct. 14, 1969 R. E. HAYES3,471,984

BUILDING PANEL STRUCTURE Filed Dec. 8. 1966 2 Sheets-Sheet 2 Fig.3

48 3 INVENTOR.

17086797 5. HAVE-5 United States Patent 3,471,984 BUlLDlNG PANELSTRUCTURE Robert E. Hayes, Rome, Ga., assignor to Stress-Plus, Inc.,Rome, Ga., a corporation of Georgia Continuation-impart of applicationSer. No. 469,087, July 2, 1965. This application Dec. 8, 1966, Ser. No.611,503

Int. Cl. E04b 2/56, 2/06; E04c 2/02 U.S. Cl. 52309 9 Claims ABSTRACT OFTHE DISCLOSURE A prefabricated building panel structure of thesandwich-type having a filler core interposed between two skin elementsand in which at least one shear block member is additionally securedbetween the skin elements at an intermediate transverse position todevelop unusual strength in the panel structure without any need for ordependence on perimeter framing of any sort.

Cross-reference to related application This application is acontinuation-in-part of my copending application Ser. No. 469,087, filedJuly 2, 1965, now abandoned.

Background of the invention The invention is concerned withprefabricated building panel structures of the sandwich-type that ditferover the prior art by incorporating at least one transversely ar rangedshear block member positioned intermediate the panel ends and serving toinvest the panel structure with exceptional strength, while beingproportioned to remain clear of any side edge jointing means employed inor with the panel for installation purposes.

No comparable proposal has been found in the prior art, the state ofwhich is believed to be fairly illustrated for present purposes by:Kloote, 2,199,938, May 7, 1940; Boyer, 2,376,653, May 22, 1945; Keller,3,161,267, Dec. 15, 1964.

The Kloote disclosure is concerned with a panel structure in which theemphasis is on the integration of intermediate ribbing with perimeterframing, and in which the intermediate ribbing is closely spaced toprovide aggregate strength from the ribbing, rather than attempting todevelop the full strength potential of the skin elements with a minim-umof framing. Additionally, the panels contemplated by Kloote, which areintended for aircraft flooring, are notably of relatively limited sizeboth as to thickness and as to length and breadth.

The Boyer disclosure describes a laminated board having a thickness inthe order of A inch in which stiffening spacers may be used, but inwhich the spacers are apparently, as in Kloote, closely spaced when theyare used. Also, Boyer describes his skin elements as sheets without anyindication that they are intended to have significant strength of theirown.

Finally, the Keller disclosure shows a building panel structure in whicha stiifening core frame, that includes perimeter framing, is providedfor fitting with skin elements at one or both faces. When skin elementsare used at both faces, they are not connected other than through theframing, and the framing is purposely depended on for strength so thatthinner, and consequently less expensive, skin elements may be used.

The present invention renders any special stiffener framing unnecessaryand makes it possible instead to increase substantially the utility ofconventional sandwich-type panels through the addition of at least onetransversely arranged shear block member.

3,471,984 Patented Oct. 14, 1969 Summary of the invention Buildingpanels of the sort dealt with by the present inventioncharacteristically comprise a pair of skin elements having a filler coreinterposed in sandwich fashion. The filler core is employed essentiallyas a spacing means between the skin elements. The filler may beadditionally selected for thermal insulation purposes, but the fillercore materials commonly used are all of low density to maintain theircost within reason, and of consequently limited physical strength. Allof these materials have sufficient compressive strength to serve theirfilling or spacing function when used properly, but none of them haveany appreciable strength in tension or shear.

As a result, the skin elements must be depended on to provide thestrength required in the panel structure, and the advantage at which theskin elements can be employed for this purpose determines not only theutility of the paenel structure but the reasonableness of its cost aswell, for a favorable cost balance is promoted by maintaining therelatively expensive skin elements as thin as possible. As a generalrule, a favorable cost balance cannot be obtained unless the skinelements represent no more than about 10% to 25% of the mass or volumeof the panel structure.

These considerations have heretofore severely limited the uses to whichprefabricated building panels might be put. For example, exterior wallpanels are commonly subject to design specifications requiring a degreeof stifiness for withstanding wind loading that could not be met by thesandwich-type panel structures previously available. The same thing istrue with respect to the load capability normally specified for roofpanels.

The present invention makes it possible to comply with such designspecifications readily by additionally including at least one shearblock member secured between the skin elements at an intermediate,transverse position with respect to the span closing dimension of thepanel structure; that is, the panel structure dimension which isproportioned for installation across the span at which deflectionloading must be borne. The transversely positioned shear block member isinterposed between the skin elements together with the filler core, andWhether more than one shear block member is used depends on the extentof span to be closed and the degree of deflection loading to be borne.If the span to be closed exceeds 8 feet, or if the panel structure isrequired to withstand deflection loading of 30 pounds per square foot ormore, there should be more than one shear block member provided. Thenumber of shear block members to be provided is determined by theaggregate shear block width required to prevent slipping of the skinelements with respect thereto under the forces resulting from deflectionloading normal to the exterior face of either of the skin elements,while limiting the individual shear block width to about three-fifths ofthe shear block depth. The shear block depth, of course, correspondswith the filler core depth, and is determined by the size of panelsection needed for the purpose at hand.

It has already been noted that at least one shear block member is alwaysused. As many as five might be employed advantageously in exceptionallylarge panels, but no more than three are needed under usualcircumstances. When only one shear block member is used, it should belocated transversely at the longitudinal center of the panel. Absolutecentering is not essential, for a lessened but still materialstrengthening is obtained at locations considerably off-center, but thebest advantage results when a practical centering of the shear blockmember is maintained. If the length of the panel structure indicatesthat more than one shear block member is needed, two such membersequally spaced lengthwise of the panel may be used, as

in the illustrated embodiment that is described further below, when thepanel structure involved has a margin of ultimate strength so thatresistance to deflection is the determining design factor. That is, whenthe object is simply to make certain that maximum deflection will remainbelow a certain limit under a specified loading. On the other hand, whenmaximum ultimate strength is needed or desired in a given panelstructure, a centrally located shear block member should be used withsupplementing additional shear block members spaced to each side asneeded for maintaining deflection strength Within specified oracceptable limits when the length of the panel of the expected loadingrequires such supplementing. In such a case, the additional shear blockmembers are equally or symmetrically spaced to each side of the centralone so as to have a related transverse location at which they serve tosupplement the strengthening action of the central member as determinedby stress analysis of the particular panel structure at hand. Thesymmetrical spacing of the additional shear block members to each sideof the central one will always be substantial, but it will vary from onepanel design to another, and it will not necessarily coincide with themidpoint between the central member and the panel ends. A practicalguide for location of the additional shear block members under usualdesign conditions is given by the formula:

where X is the spacing from the longitudinal center of the panel atwhich the additional members should be located, S is the thickness ofone skin element, A is half the panel length, and B is the aggregatethickness of the core and one skin element; all in inches. Thus, in 4 x8' panels employing a 2" core, the X spacing should be about 28" withMs" skin elements; about 34" with 7 skin elements; and about 38% with A"skin elements. Such spacing is not precisely critical, but the formulaindication points to the best results and there is advantage infollowing it, when the indicated X dimension is within onehalf of panellength.

The shear block members are suitably formed of wood and are proportionedin cross-section so that their width is neither less than the previouslynoted three-fifths relation to depth nor greatly in excess of thisrelation. A crosssection of 2 /2" x 1%" has been used to good advantagein panel structures formed of A" skin elements on a 2 /2 filler core.The shear block members are proportioned in length so that they extendtransversely for at least 75 percent of the transverse panel structuredimension but terminate short of the skin element side edges and alsoshort of any panel jointing means disposed thereat, and they are securedbetween the skin elements by an adhesive developing a bond at the innerskin element faces of greater strength than the skin elements or theshear block member.

As will appear more fully below, exterior wall panels of the foregoingsection dimensions have been successfully prepared according to thepresent invention to comply with a design specification for withstandinga uniform wind load of 45 p.s.f. with a deflection limited to the spandivided by 240, which is considerably beyond the capability ofprefabricated sandwich-type panels otherwise available. It is notunderstood exactly why the use of shear block members in the mannerindicated above produces the marked increase in panel strength that hasbeen observed. It appears possible that the shear block members causethe skin elements to act as a composite beam and thereby develop thefull strength of the skin element that is tensioned by the deflectionloading imposed. This possibility is suggested by the fact that underdeflection test loading to destruction the tensioned skin element ofpanel structures embodying the present invention has been observed tofail ultimately in tension, without any evidence of appreciable bendingstrain. In any event, the marked increase in strength has been confirmedin actual use.

The panel structure arrangement of the present invention may be readilyarranged for jointing in a variety of ways upon installation, and thepresent invention also provides for facing such panels to uniqueadvantage, as is noted further below in describing the invention atgreater length in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a section of an installedpanel structure embodying the invention;

FIG. 2 is an elevation as seen from the right in FIG. 1;

FIG. 2a is a fragmentary side elevation of an alternative form of panelstructure in which shear blocking is employed centrally andsupplementally to each side;

FIG. 3 is an enlarged fragmentary section showing the head installationdetails substantially at the line 33 in FIG. 2;

FIG. 4 is a further fragmentary section, illustrating a suitabe sideedge jointing arrangement for the panels, as taken substantially at theline 44 in FIG. 1; and

FIG. 5 is a final fragmentary section showing the foot installationdetails substantially at the line 55 in FIG. 2.

Description of the preferred embodiments Referring now in detail to thedrawing, and more particularly at first to FIG. 1, the reference numeral10 indicates generally the disposition of a representative panelstructure embodying the present invention installed as an exterior wallmember closing the span between a floor slab 12 and a deck structure 14,with a ceiling means 16 supporting insulation 18 hung below the deckstructure 14 and the panel structure 10 being arranged with a sufiicientupward extent for fitting with a super-structure at 20 to form a balconyrailing in relation to the upper surface of the deck structure 14.

For an installation such as is illustrated in FIG. 1, the panelstructure 10 needs to be about 12 in length (not including thesuperstructure 20), and as the skin element materials are commonlyavailable in a commercially standard 4 running width the resulting unitsize of panels 10 is 4' x 12', with the direction of greater tensilestrength inherently extending with the span closing length. ComparingFIGS. 1 and 2, these panel units 10 are seen to comprise outer and innerskin elements 22 and 24 assembled on an interposed filler core(indicated fragmentarily in FIG. 1 at 26) together with the previouslymentioned shear block members arranged, as at 28 in FIGS. 1 and 2,intermediately and transversely of the length.

The skin elements 22 and 24 are suitably, and even preferably in thisinstance, formed of steam cured asbestos-cement sheets. Uncured sheetmaterial of this sort is commercially available as Johns-ManvilleFlexboard" to meet Federal Specification SS-B-755, Type F; and ASTMSpecification C220-61 Type F. Steam curing of this sheet materialimproves its physical strength appreciably and adapts it for use toexcellent advantage according to the present invention. For theillustrated exterior wall use, the steam cured asbestos-cement sheetsare provided in Mt thickness, while /8 thickness would be sufficient forinterior wall use. The A skin elements 22 and 24 are assembled on a 2/2" filler core 26 to form a composite panel thickness of 3", andextruded bead expanded cellular polystyrene is employed as the corematerial to afford adequate exterior wall thermal insulation. A core ofthis sort is capable of providing an air to air (U) value of .095, andhas the further advantage of a suitably low flame spread rating (i.e.,not more than 25 based on ASTM Specification E84-61).

The shear block members 28 are conveniently and suitably formed of woodand are used in the illustrated panel 10 at the previously mentionedcross-section dimensions of 2 /2" x 1%", with two such members beingused in view of the relatively long span to be closed between the floorslab 12 and deck structure 14, as well as the relatively high deflectionloading to be borne. It is not necessary that wood be used for the shearblocking, for any other material of comparable physical strength wouldserve as well, but wood will usually have the cost advantage for thispurpose and will usually be the easiest to handle. In using wood for theshear blocking, it should be pressure treated for flame-proofing.

The panel unit assembly is secured with adhesive, the entire inner facesof the skin elements 22 and 24 being coated with adhesive for bonding tothe filler core 26 as well as the shear blocking 28. The adhesive usedshould be highly Water and mould resistant and capable of meeting allcommercial standards for Type 2 glue lines and, in particular, FederalSpecification MMM-A-l25. A resorcinol adhesive has been found suitable.

Assembly of the illustrated panel unit 10 also includes securing oneside edge jointing block 30 in place (compare FIGS. 2 and 4), as well asan upper anchor bolt block 32 and leg portion 34 of the superstructuretogether with a stringer 36 reaching therebetween (compare FIGS. 2 and3). It will be noted that the shear blocking 28 extends transverselyshort of the jointing block 30 and of the opposite panel side so as toremain clear as the panels 10 are jointed during installation (see FIG.4).

FIG. 2a illustrates an alternative panel unit assembly of the previouslynoted 4 x 8' size in which transverse shear blocking 28' is installed atthe longitudinal center of the panel structure and at two supplementinglocations spaced substantially and equally toward the panel ends at eachside. As in the FIG. 2 embodiment, a side edge jointing block 30' issecured between the skin elements (only the outer of which, 22, isshown), while the shear blocking 28 terminates short of the jointingblock 30 in each instance, and the panel structure is completed byinterposed filler core material as indicated at 26'.

FIGS. 3 and 4 indicate the ease with which the panel units 10 can beerected and fixed in place. FIG. 5 shows the floor slab 12 fitted bymeans of anchor studs, as at 38, with a perimeter framing block 40 overwhich the lower open edge of the panel unit 10 is simply set in placewithout needing any fastening thereat whatever. The only fasteningemployed is at the previously mentioned anchor bolt block 32 at which ananchor bolt 42 is employed for connection with an attaching plate 44anchored in turn, as shown, in the deck structure 14.

As each panel unit 10 is erected in this manner, it is jointed with thepreviously erected one by nesting its side edge jointing block 30 withinthe open side edge of the adjacent panel, or vice versa, to form a sideedge joint as illustrated in FIG. 4. If the resulting joint must be madewaterproof in the course of formation, a suitable adhesive is used insecuring the joint. Otherwise, the simplest procedure is simply tofasten the joint preliminarily with nails as indicated at 46.

Panel units 10 embodying the present invention have been prepared andarranged in the foregoing manner for exterior wall use to meet thepreviously noted design requirements of withstanding a uniform wind loadof 45 p.s.f, with deflection limited to the span divided by 240, andadditionally providing a safety factor of three to one at design load,while also affording an exceedingly attractive cost balance both fromthe standpoint of first cost and erection handling.

The panel arrangement illustrated has also been uniquely provided,according to the present invention, with a decorative aggregate facingas indicated at 48 in FIGS. 3, 4 and 5. The facing used in this instancewas formed with a size #2 quartz aggregate; although the same thingmight be done with a marble aggregate, a variety of gravels, or anyother material of this sort. Application of the aggregate 48 isaccomplished with an epoxy adhesive matrix having a thickness of about/8" to and most of the application is done during prefabrication of thepanel units 10 with a self-leveling formulation suitably comprising (byvolume):

Parts Epoxy resin (H.B. Fuller #7377) 13 Catalyst for the epoxy resin l#4 silica sand l3 #8 marble dust 4 After suitable catalyst activationand blending of the silica sand and marble dust extenders, the epoxymatrix may be applied with a hand trowel or any other convenientspreading means. Once the matrix is in place, aggregate facing is simplysprinkled thereon at a proper facing distribution and then tamped to asecure seating in the matrix with a rubber-faced float or the like.During such facing of the panels 10 in the course of prefabrication,side edge portions of the treated panel surface are left clear for jointcovering, in a width of the order indicated at 48 in FIG. 4, after thepanels 10 have been erected. For the joint covering aggregateapplication after erection, the epoxy matrix formulation should bemodified sufiiciently to stand properly on a vertical surface, An epoxyresin of the type of HE. Fuller #167 is suitable for such modification.

Use of the epoxy matrix for application of the aggregate facing 48provides the unusual result, when the skin elements 22 and 24 areasbestos-cement sheet, of leaving the balance of the panel structureundisturbed despite addition of the facing 48 at the exterior surfacethereof. That is, the respective skin elements 22 and 24 are allowed tofunction normally as the paired surface components that give the panelunit 10 its structure strength without hindrance from the facing 48.Such a result is not usually possible because a facing addition commonlytends to modify substantially the response of a skin element on which itis applied to the physical conditions that the skin element must bear.For example, a facing addition will ordinarily impose a bucklingtendency on a skin element during thermal expansion or contraction, andit may change materially the flexibility or stiffness of the skinelement, so that the structural action of the faced skin element is nolonger paired with its partner.

An epoxy matrix obviates any such difliculty, apparently by suchphysical compatibility with asbestos-cement sheet as to allow such sheetto function as a skin element substantially as if it were not faced andthereby preserve the structural balance of the panel unit. The epoxymatrix also affords the characteristic adhesive strength of suchmaterials for durable application of the aggregate facing 48, andadditionally serves effectively for waterproofing the panel joints uponjoint covering application at 48.

FIG. 3 further indicates the manner in which the aggregate facing 48 maybe carried over the upper exposed end portion of the pnaels 10 withadditional abbreviated asbestos-cement pieces 24 and 24" laminated onthe inner skin element 24 to provide a sheltering cavity in which asealing cover 50 for the deck structure '14 may be terminated. It shouldalso be noticed in FIG. 5 that the lower edge of the outer skin element22 may suitably be extended slightly to provide for sheltered caulkingas at 52 in relation to the floor slab 12.

Finally, it should be mentioned that panel structures embodying thepresent invention may be formed with a great variety of materials otherthan those that have been specifically noted. For example, when roofpanels are to be formed, it will usually be desirable to use plywoodskin elements. Other exemplary skin element materials that may be usedare gypsum board, gypsum form board, laminated paperboard (vinyl coated,if desired), and the like. A wide choice of other core materials islikewise available, such as expanded bead polystyrene, urethane foam,and paper honeycomb materials.

The present invention has been described in detail above for purposes ofillustration only and is not intended to be 7 limited by thisdescription or otherwise except as defined in the appended claims.

Iclaim:

1. In a structure having members defining a structural span at whichdeflection loading must be borne by closing means thereat, thecombination with said members of: an improved panel structure forclosing said span which consists essentially of a pair of skin elements;and a filler core interposed between said skin elements together with atleast one shear block member; all such shear block members being securedagainst slippage to the respective inner faces of said skin elements atan intermediate, transverse position With respect to the span closingdimension of said panel structure that is related to the midpoint ofsaid dimension, extending transversely and continuously for at least 75percent of the transverse dimension of said panel structure butterminating short of the skin element side edges and of any paneljointing means thereat, and having in sum the physical strength towithstand the shear stresses generated parallel to said skin elementsand perpendicular to the longitudinal axis of said shear block membersby the deflection loading that must be home at said span.

2. The combination as defined in claim 1 and further characterized inthat all such shear block members have a depth corresponding to thedepth of said filler core and a width not less than and not greatlyexceeding three-fifths of said depth.

3. The combination as defined in claim 1 and further characterized inthat all such shear block members are adhesively secured to therespective inner faces of said skin elements, and the number of shearblock members provided is determined by the aggregate shear block widthrequired to prevent slipping of the skin elements with respect theretounder the stresses resulting from deflection loading normal to theexterior face of either of said skin elements.

4. The combination as defined in claim 3 and further characterized inthat the transverse positioning of all shear block members provided isequally spaced intermediatelly of said span closing dimension.

5. The combination as defined in claim 3 and further characterized inthat three shear block members are provided with one transverselylocated at the longitudinal center of the panel structure and the othertwo spaced substantially and equally to each side of said longitudinalcenter at supplementing transverse locations.

6. The combination as defined in claim 1 and further characterized inthat said skin elements are formed of steam cured asbestos-cementsheets.

7. The combination as defined in claim 1 and further charzgterized inthat said filler core is formed of expanded cellular polystyrene.

8. The combination as defined in claim 1 and further characterized inthat all such shear block members are formed of wood.

9. The combination as defined in claim 1 and further characterized inthat the exterior face of at least one of said skin elements has anaggregate facing applied thereto with an epoxy matrix.

References Cited UNITED STATES PATENTS 2,376,653 5/1945 Boyer 52-309 X3,363,378 1/1968 Palfey 52-615 2,660,766 12/1953 Petterson 52-6152,725,604 12/1955 Loetscher 52-615 2,791,809 5/1957 Lincoln 52-615 X2,858,580 11/1958 Thompson 52-309 X 2,872,710 2/1959 Cox 52-615 X3,226,902 1/1966 Elmendorf 52-615 FOREIGN PATENTS 25,221 1952 Finland.680,240 1964 Canada. 236,934 1961 Australia.

OTHER REFERENCES House & Home, vol. XVII, No. 1, January 1960, p. 156.

Architectural Record, vol. 133, No. 5, May 1963, p. 325.

American Builder, October 1950, p. 60.

JOHN E. MURTAGH, Primary Examiner U.S. Cl. X.R.

